A diamond drilling tool for mining is a tool that is used to bore several tens to several thousands of meters into the ground to extract a core sample (a cylindrical sample taken lengthwise from drilled bedrock), in order to check the distribution or buried quantity of useful minerals in the ground.
As shown in FIG. 1, a diamond drilling tool 1 for mining can be largely divided into a core bit 10 and a reaming shell 20, where the core bit 10 is a tool that directly contacts bedrock containing minerals to excavate (drill) the bedrock, and the reaming shell 20 is a tool connected directly to the rear of the core bit 10 to perform a finishing operation on the uneven portions of the bedrock drilled by the core bit 10 to make the gauge of the bedrock uniform.
When a diamond drilling tool for mining is used for excavating bedrock, it is very important to maintain a uniform hole diameter of the bored bedrock (the function of a reaming shell), because if the bored diameter of the bedrock is not uniform along its length from the tip to the mining drilling machine on the ground surface connected by pipes (drilling rods supplied with cooling water), the pipes connected in between are prone to be damaged, and the excavating speed (drilling speed and cutting ability) are affected.
Therefore, the function of the reaming shell that maintains hole diameter during drilling is very important, and the durability of the reaming shell determines how long the hole diameter can be uniformly maintained during drilling.
An example of a related art reaming shell is shown in FIG. 2, where a large quantity of cooling water supplied to the core bit 10 during drilling is supplied within the core bit 10 that performs the excavation, through a pipe (drilling rod), after which bedrock particles cut by the core bit 10 are externally discharged with the water.
The thus-discharged drilling sludge (cooling water+bedrock particles) is discharged toward the reaming shell whose outer periphery with a water way between one pad 21 and another pad 21 is substantially the same as the outer periphery of the shank 201, so that the drilling sludge cannot easily be discharged.
Thus, drilling sludge is not easily discharged with a related art reaming shell, inducing the formation of drilling slurry vortices at the leading edge 23 of the reaming shell 20, leading to localized wear and resultant early wear or separation of grinding material 211, and ultimately causing the inability to maintain hole diameter uniformity and a significant reduction in service life.